1. Field of the Invention
The present invention relates generally to loose-leaf binders that provide the releasable insertion of sheets of paper, and more particularly, to an improved and simplified binding system for loose-leaf sheets of paper that securely retains loose-leaf paper while enabling removal and addition of paper bound by the system.
2. Description of Related Art
Loose-leaf or ring binders for holding sheets of paper are well known in the art. These binders typically comprise front and back covers hingably connected to a spine. The spine usually comprises a metal or hard plastic and includes a plurality of spatially positioned two piece rigid rings for retaining the sheets of paper. The rings are opened and closed for adding and removing paper from the binder, and comprise known configurations such as annular or D-shaped, for example and rigid materials, such as steel or aluminum.
However, a disadvantage common to these binders, is that the rings have a fixed diameter, to accommodate a desired maximum amount of paper to be held by the binder. The spine is typically wider than the diameter of the rings, so that paper may be easily added or removed from the binder. Thus, the spine is substantially wider than the open end of the binder which gives the binder a triangular cross-sectional configuration, with the front and back covers extending obtusely toward each other from the wide spine. The triangular cross-sectional configuration makes it somewhat difficult to stack a number of these binders on top of each other, and additionally, it is difficult to place the binders adjacent to books on a bookshelf, due to the angularity of the binders. Further, since the rings are a fixed diameter and the spine is a fixed width, a substantial amount of space, such as shelf space on a bookcase, is wasted when the binder is not full of paper.
Devices in the prior art have attempted to overcome some of the disadvantages of ring binders. One such device is disclosed in U.S. Pat. No. 4,369,013, to Abildgaard et al., which teaches bookbinding strips. The disclosed strips are provided with plastic studs which fit through holes vicinal one margin of each sheet of paper. The studs may be integrally formed in one strip, or may be alternating in both strips. Holes are provided in one strip, or both strips, for receiving the studs. Excess stud lengths are sheared and headed to lock the strips and sheets of paper interposed between the strips in position. A disadvantage of the disclosed device, is that once the studs are sheared and headed, papers cannot be added or removed from the binding system, without destroying some component of the system necessitating the installation of new strips. Also, when many papers are bound by the disclosed device, the bound pages are substantially difficult to spread open and lie flat due to the stiff spine formed by the studs extending between the strips, making it difficult to read text adjacent to the spine of the device.
Another binding device is disclosed in U.S. Pat. No. 5,213,370, to Hood, which is directed to an expandable loose-leaf volume. The disclosed volume comprises an expandable spine that may be incorporated into a loose-leaf photograph album or binder. The spine has an expansion means which allows the user to increase or decrease the capacity of the spine to match the volume of the contents. A flexible material covers the spine to give it the appearance of a bound book. Between the expansion means and the flexible material is a resilient material that serves as a means to compensate for the change in width of the spine so that the flexible material remains smoothly fitted to the spine. In this way the spine maintains the appearance of a bound book at any state of expansion. An album incorporating the spine also includes a page retaining means which is attached to the spine and a front and back cover which are hinged to the spine.
U.S. Pat. No. 5,242,236, to Isac, is directed to a holder for holding a plurality of sheets formed with holes adjacent to one of their edges. The holder includes a backing member and a pair of slides. The slides are slidable along each end of a track that extends along the width of the upper end of the backing member. The holder includes cords that have mating connectors at one end to permit the plurality of sheets to be secured to a length-varying device. The length of the cords can be varied according to the number of sheets to be secured by the cords. The length-varying device comprises a long portion of VELCRO.RTM. retained in the track. Mating portions of VELCRO.RTM. are secured to the cords and detachably coupled to the track, for adjusting the length of the cords. A disadvantage of the disclosed holder, is that it is difficult to remove or add paper to the holder because the cords are flaccid. Further, the two piece cords must be separated or when adding or removing paper, similar to that of conventional ring binders.
U.S. Pat. No. 2,879,772, to Murphy et al., discloses a loose-leaf binder that includes a pair of retainer members, each comprising a length of flexible wire, such as piano wire. A disadvantage of the disclosed binder, is that the retainer members each comprise a closed loop, which extends substantially above the plane of the upper surface of the cover. Thus, the binders are not well suited for stacking on top of each other or for placing the binders adjacent to books on a bookshelf, a disadvantage similar to that of ring binders.
Additional loose-leaf binders are disclosed in U.S. Pat. No. 2,372,717, to Federn; U.S. Pat. No. 2,007,763, to Klein; U.S. Pat. No. 1,548,147, to Leach; and U.S. Pat. No. 4,775,257, to Rigg.
There, therefore exists a need for an improved and simplified binding system for loose-leaf sheets of paper that securely retains the paper and that provides facile removal and addition of papers bound by the system, and further enables front and back covers thereof to extend substantially parallel to each other regardless of the quantity of paper bound by the binding system.